Systems and Methods for Uplink Power Control and Scheduling in a Wireless Network

ABSTRACT

Methods and systems for facilitating uplink power control (PC) and scheduling in a wireless network are provided. In one example, common interference patterns are obtained from long term channel statistics, and used to perform local PC and scheduling by distributed base stations (eNBs). In some implementations, the common interference patterns are obtained through statistical narrowing techniques that identify common ones out of a plurality of potential interference patterns. The common interference patterns may specify maximum interference thresholds and/or individual eNB-to-eNB interference thresholds which may govern the local PC and scheduling decisions of the distributed eNBs.

This patent application is a continuation of U.S. Non-Provisionalapplication Ser. No. 13/650,658, filed on Oct. 12, 2012 and entitled“Systems and Methods for Uplink Power Control and Scheduling in aWireless Network,” which is hereby incorporated by reference herein asif reproduced in its entirety.

TECHNICAL FIELD

The present invention relates generally to wireless communications, and,in particular embodiments, to optimizing uplink power control andscheduling in wireless communication systems.

BACKGROUND

Modern day wireless communications employ various techniques to regulateinterference in an attempt to achieve desired levels of coverage andthroughput. One significant challenge is mitigatinginter-cell-interference (ICI) in the uplink communications channel,where link adaptation and channel estimation tends to be more complexdue to the shifting of uplink transmission points from one resourceblock (RB) to another.

One technique for mitigating ICI in the uplink channel is to coordinateuplink power control (PC) and scheduling decisions amongst neighboringbase stations (eNBs). Generally speaking, uplink PC regulates thetransmit power for signals propagated in the uplink channel, whileuplink scheduling regulates the allocation of uplink time-frequencyresources to candidate user equipments (UEs). Conventionally, uplinkpower control (PC) and scheduling may be coordinated in a centralizedfashion by delegating PC/scheduling decisions to a centralizedcontroller. Specifically, the centralized controller may dynamicallyperform joint power control (JPC) and/or joint scheduling (JS) using anexhaustive search approach, thereby generating a global PC/schedulingsolution that (at least theoretically) achieves optimal coverage andthroughput in the wireless network. However, this centralized approachto uplink PC and scheduling may consume relatively large amounts ofnetwork resources (e.g., bandwidth, processing, etc.), particularly inlarge networks that include many eNBs. In some instances, networkshaving limited resources to devote to PC/scheduling may find centralizedPC/scheduling to be impractical or infeasible. As such, more efficientalternatives for effectively mitigating ICI in uplink communicationchannels are desired.

SUMMARY OF THE INVENTION

Technical advantages are generally achieved, by preferred embodiments ofthe present invention which describe system and methods for optimizingdownlink power control.

In accordance with an embodiment, a method for facilitating uplink powercontrol (PC) and scheduling in a wireless network is provided. In thisexample, the method comprises generating potential interference patternsin accordance with long term channel statistics, statistically narrowingthe potential interference patterns into one or more common interferencepatterns, and sending the one or more common interference patterns to aneNB for use when performing localized PC and scheduling. In accordancewith another embodiment, a central controller is provided for performingthe above mentioned method.

In accordance with yet another embodiment, an eNB of a wireless networkis provided. In this example, the eNB is configured to receive a commoninterference pattern from a central controller, and performing localizedscheduling and PC with respect to the common interference pattern. Inembodiments, the localized scheduling and PC may be performed byidentifying a plurality of individual eNB-to-eNB interference thresholdsof the common interference pattern, and scheduling uplink transmissionsby candidate UEs without exceeding those individual eNB-to-eNBinterference thresholds.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 illustrates a diagram of a wireless network architecture;

FIG. 2( a) illustrates a diagram of a scheduling scenario for a wirelessnetwork;

FIG. 2( b) illustrates a diagram of a simulated PC/scheduling solutionfor the scheduling scenario depicted in FIG. 2( a);

FIG. 2( c) illustrates a diagram of a set of interference componentsresulting from the simulated PC/scheduling solution depicted in FIG. 2(b);

FIG. 2( d) illustrates a diagram of another set of interferencecomponents resulting from the simulated PC/scheduling solution depictedin FIG. 2( b);

FIG. 2( e) illustrates a diagram of yet another set of interferencecomponents resulting from the simulated PC/scheduling solution depictedin FIG. 2( b);

FIG. 3 illustrates a graph of total interference thresholds resultingfrom the simulated PC/scheduling solution depicted in FIG. 2( b);

FIG. 4 illustrates a diagram of an embodiment of an interferencepattern;

FIG. 5 illustrates a diagram of another embodiment of an interferencepattern;

FIG. 6( a) illustrates a diagram of path loss characteristics in awireless network;

FIG. 6( b) illustrates a diagram of some estimated interference levelsprojected to result from potential scheduling decisions;

FIG. 6( c) illustrates a diagram of other estimated interference levelsprojected to result from potential scheduling decisions;

FIG. 7 illustrates a flowchart of method for performing distributed PCand scheduling in accordance with a common interference pattern;

FIG. 8 illustrates a flowchart of a method for obtaining a commoninterference pattern;

FIG. 9 illustrates a block diagram of an embodiment of a PC controller;and

FIG. 10 illustrates a block diagram of an embodiment of an eNB.

Corresponding numerals and symbols in the different figures generallyrefer to corresponding parts unless otherwise indicated. The figures aredrawn to clearly illustrate the relevant aspects of the preferredembodiments and are not necessarily drawn to scale.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The making and using of the presently preferred embodiments arediscussed in detail below. It should be appreciated, however, that thepresent invention provides many applicable inventive concepts that canbe embodied in a wide variety of specific contexts. The specificembodiments discussed are merely illustrative of specific ways to makeand use the invention, and do not limit the scope of the invention.

Aspects of this disclosure describe techniques for performingdistributed uplink PC/scheduling in accordance with a commoninterference pattern. The common interference pattern may correspond toan approximation of optimal ICI levels in the network, and may becomputed by a centralized controller using long term channel statisticsprovided by the eNBs. In embodiments, the centralized controller mayobtain the common interference pattern by simulating joint power control(JPC) and joint scheduling (JS) on potential scheduling scenarios (e.g.,likely traffic patterns, user distributions, etc.), which may beidentified by analyzing the long term channel statistics. The commoninterference pattern may be provided statically or semi-statically tothe eNBs, and may specify interference thresholds that the eNBs may use(in conjunction with path loss information of candidate UEs) to performdistributed/localized uplink PC and scheduling. For instance, thecentralized controller may statically provide the common interferencepattern to the eNBs by signaling the common interference pattern uponinitialization of the network. In some embodiments, the commoninterference pattern may be updated in an aperiodic manner, such as whenthe network is re-initialized after an outage, or upon theaddition/removal of an eNB (e.g., in which case the common interferencepattern would change). In other embodiments, the centralized controllermay provide updated/new common interference patterns to the eNBs in asemi-static manner by periodically updating the common interferencepattern in accordance with an updating period. Performing distributeduplink PC/scheduling according to one or more aspects of this disclosuremay achieve levels of coverage and throughput that rivals that achievedby conventional centralized techniques, while (at the same time)consuming significantly less network resources.

FIG. 1 illustrates a wireless network 100 comprising a plurality ofcellular coverage areas (cells) 101, 102, within which wireless accessis provided by a plurality eNBs 110, 120 (respectively). During thecourse of providing wireless access, the eNBs 110, 120 may schedule theUEs 115, 125 to perform uplink transmissions (dashed lines) in a commontime-frequency resource (e.g., the same RB). The resulting uplinktransmissions may interfere with one another, thereby producing ICI inthe cells 101, 102. Specifically, the eNB 110 may observe interferencefrom the UE 125 when receiving the uplink transmission from the UE 115,while the eNB 120 may observe interference from the UE 115 whenreceiving the uplink transmission from the UE 125. High levels of ICImay reduce coverage and throughput in the network 100, and consequently,techniques that effectively mitigate ICI may generally increase networkperformance.

FIG. 2( a) illustrates a scheduling scenario for a network 200 thatincludes a plurality of cells 201-205. As shown, the cells 201-205 housea plurality of eNBs 210-250, which provide wireless access to aplurality of candidate UEs (not labeled). A candidate UE may representany wireless device requesting uplink resources for performing uplinktransmissions in the network 200. As shown in FIG. 2( a), variouscombinations of UEs could be scheduled to perform uplink transmissionsin the cells 201-205 during a given RB, and hence a plurality ofpossible PC/scheduling solutions exist for the scheduling scenarioillustrated in FIG. 2( b). Notably, the PC/scheduling solutions havedifferent utilities, as each will produce different levels of coverageand throughput in the network 200.

To identify an optimal one of the plurality of PC/scheduling solutions,a centralized PC controller 290 may perform JPC/JS (e.g., using anexhaustive search or alternate technique) to estimate the utilities ofeach potential PC/scheduling solution. Subsequently the PC controller290 may run a simulation of the optimal PC/scheduling solution on thegiven scheduling scenario, thereby obtaining a resulting interferencepattern corresponding with that scenario. The interference pattern mayspecify ideal interference thresholds for each of the eNBs.

FIG. 2( b) illustrates a simulated PC/scheduling solution for thescheduling situation shown in FIG. 2( a). As shown in FIG. 2( b), thesimulated PC/scheduling solution includes the scheduling of a pluralityof uplink transmissions [UL₁, UL₂, UL₃, UL₄, UL₅] at appropriate powerlevels in the cells 201-205 (respectively). Each of the uplinktransmission UL₁-UL₅ may produce an interference component (e.g., anindividual eNB-to-eNB interference threshold) in one or more of theneighboring cells 201-205. For instance, FIG. 2( c) illustrates theinterference produced in the cells 201-204 as a result of the uplinktransmission UL₅ in the cell 205. As shown, the uplink transmission UL₅produces interference levels of ICI₅(C₁) in cell 201, ICI₅(C₂) in cell202, ICI₅(C₃) in cell 203, and ICI₅(C₄) in cell 204.

Likewise, the total interference observed in a given one of the cells201-205 may be a combination of the interference components resultingfrom uplink transmissions in the other cells 201-205. For instance, FIG.2( d) illustrates the total interference observed in cell 205 as aresult of uplink transmissions performed in the cells 201-204. As shown,the uplink signal (UL₅) in cell 205 is disrupted by a multi-componentICI, which includes the interference components [ICI₁(C₅), ICI₂(C₅),ICI₃(C₅), ICI₄(C₅)] attributable to uplink transmissions in the cells201-204. Notably, the uplink transmissions UL₁-UL₄ are not explicitlydepicted in FIGS. 2( c)-(d) for purposes of clarity, but arenevertheless inherently present.

Interestingly, the interference components (e.g., ICI₁(C₅), ICI₂(C₅),ICI₃(C₅), ICI₄(C₅)) may have different magnitudes based on a number offactors (e.g., path loss, transmit power, etc.) of the correspondinguplink signals UL₁-UL₄. This concept is more clearly understood withreference to FIG. 2( e), which shows the effective interference observedin cell 203 as a result of uplink transmissions in the cells 201, 202,204, 205. As shown, the uplink transmission (UL₃) communicated in cell203 is disrupted (at least partially) by a plurality of interferencesignals [ICI₂(C₃), ICI₄(C₃), ICI₅(C₃)] from uplink transmissionsperformed in each of the cells 202, 204, 205. However, the interferencecomponent ICI₁(C₃) resulting from uplink transmissions in cell 201 maybe attenuated significantly and/or completely dissipated before reachingcell 203, and therefore may produce a negligible amount of interferencein the cell 203. Notably, the uplink transmissions UL₁, UL₂, UL₃, UL₄are not explicitly depicted in FIG. 2( e) for purposes of clarity, butare nevertheless inherently present.

FIG. 3 illustrates a graph 300 of the interference produced in thenetwork 200 as a result of the optimal PC/scheduling solution depictedin FIG. 2( a). As shown, the graph shows total interference thresholds[ICI_(T)(C₁), ICI_(T)(C₂), ICI_(T)(C₃), ICI_(T)(C₄), ICI_(T)(C₅)] in thecells 201-205 as being the sum of the respective interference components(e.g., Σ_(i=1) ^(i≠x)ICI_(i) (C_(r))) from neighboring cells. Forinstance, the total interference threshold ICI_(T)(C₅) is composed ofcomponent thresholds [ICI₁(C₅), ICI₂(C₅), ICI₃(C₅), ICI₄(C₅)]. Notably,some of the uplink transmissions may produce only negligible amounts ofinterference in one or more of the neighboring cells. For instance, thetotal interference threshold for cell 203 ICI_(T)(C₃) does not includean interference component from cell 201 (e.g., no ICI₁(C₃)), whichindicates that the uplink transmission in cell 201 produces onlynegligible interference in cell 203.

For a given scheduling scenario (e.g., such as that in FIG. 2( a)), itmay generally be assumed that network performance will not besignificantly reduced so long as the scheduling/PC decisions do notcollectively produce an effective amount of interference that exceedsthe total interference thresholds resulting from the optimalPC/scheduling solution. In other words, the network performance of thenetwork 200 may be close to optimal so long as the total interferencethresholds [ICI_(T)(C₁), ICI_(T)(C₂), ICI_(T)(C₃), ICI_(T)(C₄),ICI_(T)(C₅)] are not exceeded. As such, an interference patternresulting from simulating an optimal JPC/JS solution for a commonscheduling scenario may be used to effectively set scheduling rules(e.g., interference thresholds) during distributed PC/scheduling.

FIG. 4 illustrates an interference pattern 400 as may result fromsimulating the optimal PC/scheduling solution depicted in FIG. 2( b). Asshown, the interference pattern 400 comprises a plurality of rowsrepresenting the uplink signals UL₁-UL₅ and a plurality of columnsrepresenting the cells 201-205 (denoted as C₁-C₅, respectively), withthe resulting cross-sections representing the corresponding individualeNB-to-eNB interference thresholds ICI_(i)(C_(j)). Notably, theindividual eNB-to-eNB interference thresholds ICI_(i)(C_(j)) representthe maximum allowed interference observed in a given cell (Cj) as wouldresult from a scheduled uplink transmission (UL_(i)). For instance, theindividual interference threshold ICI₃(C₅) corresponds to the maximumamount of interference occurring in cell 205 as a result of thescheduled transmission UL₃ made by the eNB 230. Hence, the eNBs 230 mayview the set of interference thresholds [ICI₃(C₁), ICI₃(C₂) ICI₃(C₄)ICI₃(C₅)] as effective rules or limitations when performing localscheduling and PC for the uplink transmission UL₃. The other eNBs210-220 and 240-250 may do the same.

From an elementary perspective, a given total interference threshold[ICI_(T)(C_(x))] may be approximately equal to the sum of theinterference components attributable to uplink transmissions inneighboring cells, e.g., ICI_(T)(C_(x))]≈Σ_(i=1) ^(i≠x) ICI_(i) (C_(x)).However, this assumes that the interference components [ICI_(i)(C_(x)),ICI_(i+1)(C_(x)), etc.) interact with one another in a purelyconstructive manner, and ignores various signal characteristics that maycause the total interference threshold ICI_(T)(C_(x)) experienced in agiven cell to be less than the sum of the interference componentsattributable to neighboring cells. For instance, a first interferencecomponent for a given cell (e.g., ICI₁(C_(x))) may interfere with asecond interference component for the given cell (e.g., ICI₂(C_(x))) ina destructive manner, such that the total interference experienced in acell is less than the sum of the interference signals, e.g.,ICI_(T)(C_(x))]<Σ_(i=1) ⁴ ICI_(i). Additionally, and as a practicalmatter, it may be unlikely that each of the neighboring eNBs willschedule transmission that max out their individual eNB-to-eNBinterference threshold, which results in the observed amount ofinterference in a given cell being significantly less than totalinterference threshold ICI_(T)(C_(x)). As such, strictly adhering to theindividual eNB-to-eNB interference thresholds may underutilize networkresources.

Further, computation and/or communication of the individual eNB-to-eNBinterference thresholds may prove difficult or cumbersome in largenetworks. For instance, a network/cluster including, say, 57 cells wouldgenerate an interference pattern comprising a 57×57 matrix. Such a largeinterference pattern may consume relatively large amounts ofprocessing/backlink resources, as well as introduce complexity intooptional statistical narrowing techniques applied by the centralcontroller (discussed in greater detail below).

To address these and other issues, an interference pattern may beadapted to include only a total interference thresholds (i.e.,ICI_(T)(C_(x))) for each cell, which may be adjusted by the eNBs uponreception to obtain their effective individual eNB-to-eNB interferencethresholds. Notably, effective individual eNB-to-eNB interferencethresholds may be similar to the pre-defined individual eNB-to-eNBinterference thresholds discussed above, except that effectiveindividual eNB-to-eNB interference thresholds may be computed byreducing the total interference thresholds (i.e., ICI_(T)(C_(x)) by amargin (while pre-defined individual eNB-to-eNB interference thresholdsmay be communicated by the central controller). Unless otherwise stated,the term individual eNB-to-eNB interference thresholds may refer to bothpre-defined individual eNB-to-eNB interference thresholds and effectiveindividual eNB-to-eNB interference thresholds. FIG. 5 illustrates aninterference pattern 500 as may result from simulating the optimalPC/scheduling solution depicted in FIG. 2( b). As shown, theinterference pattern 500 includes a plurality of total interferencethresholds [ICI_(T)(C₁), ICI_(T)(C₂), ICI_(T)(C₃), ICI_(T)(C₄),ICI_(T)(C₅)] for the cells 201-205. A total interference thresholdICI_(T)(C_(x)) of a given cell (C_(x)) may be adjusted by neighboringeNBs to identify their effective individual eNB-to-eNB interferencethresholds. For instance, a given eNB may reduce a given interferenceICI_(T)(C_(x)) by a fixed or variable margin (e.g., Δm) to obtain aneffective individual eNB-to-eNB interference threshold. In oneembodiment, the margin (Δm) may be fixed at about six decibels (6 dBs).In other embodiments, the margin (Δm) may be variable, and may depend ona variety of factors (e.g., the proximity of the interference producingcell to the interference observing cell, a detected amount of temporalfading, etc.). The effective individual eNB-to-eNB interferencethresholds (e.g., which are achieved by adjusting the total interferencethreshold ICI_(T)(C_(x)) by a fixed or variable margin) may achieve amore-efficient utilization of network resources than strict adherence toindividual eNB-to-eNB interference thresholds that are pre-defined by acentralized controller.

Upon identifying a set of individual eNB-to-eNB interference thresholds(effective, pre-defined, or otherwise), the eNB may determine path losscharacteristics associated with candidate UEs. These path losscharacteristics may be used in conjunction with the set of effectiveindividual eNB-to-eNB interference thresholds to perform localizedPC/scheduling. FIG. 6 illustrates a network 600 comprising a pluralityof cells 603-605 housing a plurality of eNBs 630-650. The eNB 650 may bein the process of performing local PC/scheduling according to aninterference pattern that specifies interference thresholds for thecells 603-604. Notably, localized PC and scheduling may include variousother actions beyond selection of a transmit power level and/orassignment of time-frequency resources, such as Modulation Coding Scheme(MCS) adaptation, pre-coding, antenna direction beamwidth changes, etc.Under such schemes, local scheduling may still be performed with localpre-coding or antenna direction selection to satisfy interferenceconstraints. An exception may exist when two eNBs perform soft combiningfor a user, in which case the respective ICI thresholds may be ignoredby the two eNBs.

Specifically, the eNBs 650 may have the option of scheduling a firstcandidate UE (UE1) or a second candidate UE (UE2) to a given RB. TheeNBs 650 may first learn the path loss characteristics (PL₁₃, PL₁₄,PL₁₅, PL₂₃, PL₂₄, PL₂₅) corresponding to the UE1 and UE2 using a varietyof methods (e.g., probe signaling, etc.). Specifically, PL₁₃ mayrepresent the path loss between UE1 and eNB 630, PL₁₄ may represent thepath loss between UE1 and eNB 640, PL₁₅ may represent the path lossbetween UE1 and eNB 650, PL₂₃ may represent the path loss between UE2and eNB 630, PL₂₄ may represent the path loss between UE2 and eNB 640,PL₂₅ may represent the path loss between UE2 and eNB 650. The PL₁₅ andPL₂₅ may be used to determine the transmit power levels (TP1 and TP2,respectively) required for the UE1 and UE2 to achieve a desireddata-rate. Thereafter, the transmit power levels (TP1 and TP2) may beused in conjunction with the path loss characteristics corresponding tothe eNBs 630-640 (PL₁₃, PL₁₄, PL₂₃, PL₂₄) to determine whetherscheduling either of the UE1 or the UE2 would violate a scheduling rule,e.g., whether the effective ICI produced would exceed either one of theinterference thresholds ICI₅(C₃) or ICI₅(C₄) the cells 603-604.

FIG. 6( b) illustrates a graph 660 of the estimated interference in cell603 as projected to result from scheduling UE1 or UE2 to perform anuplink transmission in the cell 605. As shown, scheduling either UE1 orUE2 would not produce a level of interference that exceeds theindividual eNB-to-eNB interference threshold (ICI₅(C₃). FIG. 6( c)illustrates a graph 670 of the estimated interference in cell 604 asprojected to result from scheduling UE1 or UE2 to perform an uplinktransmission in the cell 605. As shown, scheduling UE1 would produce alevel of interference that exceeds the individual eNB-to-eNBinterference threshold (ICI₅(C₄), while scheduling UE2 would not producea level of interference that exceeds the individual eNB-to-eNBinterference threshold (ICI₅(C₄). As such, UE1 would be classified asunsuitable for scheduling, while UE2 would be classified as suitable forscheduling.

In one embodiment, the individual eNB-to-eNB interference thresholdsICI₅(C₃) and ICI₅(C₄) may be specified explicitly by the interferencepattern communicated by a central controller. In other embodiments, theindividual eNB-to-eNB interference thresholds ICI₅(C₃) and ICI₅(C₄) maybe obtained by adjusting total interference thresholds ICI_(T)(C₃) andICI_(T)(C₄) by a margin (Δm).

FIG. 7 illustrates a method 700 for performing distributed PC andscheduling in accordance with a common interference pattern. The method700 may begin at step 710, where an eNB may receive a commoninterference pattern from a central controller. In an alternativeembodiment, the eNB may compute a common interference pattern usingsample points received from a central controller. Next, the method 700may proceed to step 720, where the eNB may identify individualeNB-to-eNB interference thresholds for one or more of the neighboringcells, e.g., [ICI_(x)(C_(i)), ICI_(x)(C_(i+1)), . . . ] (where i≠x). Inone embodiment, the individual eNB-to-eNB interference thresholds may beexplicitly specified by the interference pattern. In other embodiments,the individual eNB-to-eNB interference thresholds may be computed byadjusting the total interference thresholds (e.g., as specified by theinterference pattern) by an appropriate margin. Thereafter, the method700 may proceed to step 730, where the eNB may identify candidate UEs(e.g., UEs requesting the allocation of uplink resources). Thereafter,the method 700 may proceed to step 740, where the eNB may identify pathloss characteristics corresponding to the candidate UEs. These path losscharacteristics may include a path loss from each candidate UE to eachneighboring eNB, and may be determined in a variety of ways (e.g.,through pilot signaling). In some embodiments, some of the path losscharacteristics may be communicated by neighboring eNBs or a PCcontroller via a backhaul connection. In the same or other embodiments,some or all of the path loss characteristics may be communicated via thecandidate UEs via a control channel.

Next, the method 700 may proceed to step 745, where the maximum transmitpower for each candidate UE is found. The maximum transmit power levelmay correspond to the highest transmit power level that does not produceinterference in excess of the ICI thresholds, and may be determined inaccordance with, inter alia, path loss characteristics. Thereafter, themethod 700 may proceed to step 750, where suitable candidate UEs may beidentified in accordance with their maximum transmit power levels.Specifically, the maximum transmit power level for some candidate UEsmay be so low as to prevent the UE from engaging in a meaningfulcommunication (e.g., from achieving a minimum bit-rate needed forsatisfactory throughput). In such embodiments, these candidate UEs maybe eliminated from consideration (e.g., classified as unsuitable). Forinstance, the UE1 (in network 600) would be classified as unsuitable, asthe amount of interference produced from the UE1's uplink transmissionwould exceed the interference threshold ICI₅(C₄) even for a smalltransmit power level. However, UE2 (in network 600) would be classifiedas suitable, as the amount of interference produced from the UE2'suplink transmission would not exceed either of the interferencethresholds ICI₅(C₃) or ICI₅(C₄) for a reasonable transmit power.Thereafter, the method 700 may proceed to step 760, where the instanteNB may select one of the suitable candidate UEs for scheduling. In anembodiment, the selection may be performed to maximize a utility, or inaccordance with some fairness computation. For this purpose, theexpected data rate could be evaluated with knowledge of the allowedmaximum transmit power, the path loss to serving base station, theexpected interference to the serving base station, or combinationsthereof. Thereafter, the expected utility could be evaluated inaccordance with the past throughput. Next, the method 700 may proceed tostep 770, where the instant eNB may communicate the scheduling decisionto the selected UE. Finally, the method 700 may proceed to step 780,where the instant eNB may determine whether or not it is time to updatethe common interference pattern. In embodiments, this determination maydepend on whether an updated interference pattern has been received fromthe central controller. In the same or other embodiments, a sequence ofcommon interference patterns may be used in a pre-defined order. Forinstance, two or more interference patterns may be used in a round robin(or alternate fashion). If it is time to update the common interferencepattern, then the method 700 may revert back to step 710. If is not timeto update the common interference pattern, then the method 700 mayrepeat steps 730-780 until it is time to update the interferencepattern.

FIG. 8 illustrates a method 800 for generating a common interferencepattern for a network or cluster of eNBs. The method 800 begins at step810, where a central controller (e.g., a PC controller) receiveslong-term channel statistics from a plurality of eNBs. Before proceedingto the step 820, the central controller may perform further processingon the long-term statistics. Next, the method 800 may proceed to step820, where the central controller identifies likely scheduling scenariosbased on the long-term channel statistics. A scheduling scenario maycorrespond to a traffic pattern or distribution of user requestinguplink resources at a given instance (or over a given period) in thewireless network. Thereafter, the method 800 may proceed to step 830,where the central controller may generate a set of potentialinterference patterns corresponding to the likely scheduling scenarios.In one embodiment, the potential interference patterns may be generatedby simulating JPC/JS on each of the identified scheduling scenarios,thereby generating (or predicting) a resulting interference pattern forthat scenario. In some embodiments, the potential interference patternsand/or common scheduling scenarios may be pre-defined (e.g., may be apriori information) by a network administrator or system designer. Insuch embodiments, the potential interference patterns and/or commonscheduling scenarios would be retrieved from memory. Subsequently, themethod 800 may proceed to step 840, where the central controller mayutilize a statistical narrowing technique to shrink the potentialinterference patterns into one or more common interference patterns. Inother words, the central controller may use statistical narrowingtechniques (discussed in greater detail below) to remove certaininterference patterns (e.g., uncommon interference patterns) and/ormerge multiple interference patterns (e.g., redundant/correlatedpatterns) from the original set of potential interference patterns,thereby generating one or more common interference patterns. Next, themethod 800 may proceed to step 850, where the central controller maysend the one or more common interference patterns to the eNBs forutilization during distributed/localized PC and scheduling. In someembodiments, the method 800 may be performed statically, in which casethe method 800 may end at step 850. In other embodiments, the method 800may be performed semi-statically, in which case the method may revert tostep 810 after a delay 860.

As discussed above, various statistical narrowing techniques may be usedto shrink a set of potential interference patterns (e.g., IP-1, IP-2, .. . , IP-N) into one or more common interference patterns. Suchstatistical narrowing techniques may use one or more of the followingsteps. One narrowing step may be to merge redundant and/or correlatedinterference patterns. During the merging process, ICI levels of two ormore redundant/correlated interference patterns are combined to form asingle interference pattern. In one embodiment, merging may be achievedby deleting/removing the less probable interference pattern withoutaltering the ICI levels of the more probable interference pattern. Inother embodiments, merging may be achieved by combining thecorresponding ICI levels using their probabilities as weights, e.g.,(a1*ICI1+a2*ICI2)/(a1+a2), where a1 and a2 are the probabilities of eachinterference pattern. Alternative techniques for merging interferencepatterns may also be used. Redundant interference patterns may be thosepatterns having identical ICI thresholds. Correlated interferencepatterns may be patterns that have similar ICI thresholds, e.g.,IP-1[ICI_(i)(C_(x))]≈IP-2[ICI_(i)(C_(x))], etc. In embodiments,interference patterns that are substantially correlated may be thosehaving a Euclidian distance less than a threshold (E_(th)). Forinstance, a first interference pattern (IP-1) and a second interferencepattern (IP-2) may be substantially correlated if their Euclidiandistance (E(IP-1, IP-2)) is less than the Euclidian threshold (e.g.,E(IP-1, IP-2)<E_(th)).

Another narrowing step may be to remove improbable interferencepatterns. Probability may be assigned based on the number of times apattern was merged. For instance, assuming there are 500 potentialinterference patterns in the set of potential interference patterns,then each interference pattern (initially) has a probabilistic weight ofabout 0.2%. Hence, merging five redundant/correlated interferencepatterns into a single interference pattern will reduce the set ofpotential interference patterns to about 496, as well as allocate aprobalistic weight to the merged interference pattern of about 1% (e.g.,0.2% multiplied by 5). Another narrowing step may be to rank theinterference patterns (e.g., after merging) based on their probability,and (subsequently) merge less probable interference patterns. Forinstance, the more probable interference pattern may absorb the lessprobable interference patterns until enough improbable interferencepatterns have been culled. The narrowing techniques discussed herein mayinclude one or more of the above discussed narrowing steps, as well asother steps.

In some embodiments, an alternative technique for finding a commoninterference pattern may be used. For example, the centralized schememay find power patterns for N resource blocks by simulation or othermeans. Then, according to this example, a number of most probable (Np)patterns are selected for continued processing. Consequently, theremaining least probable patterns (e.g., N−Np patterns) are merged withthose selected Np patterns. There are several ways to merge the N−Nppatterns with the Np patterns. For instance, the lowest probable patternfrom N−NP patterns may be merged with the most closely matching patternin the selected group of N patterns, with the product of the two mergedpatterns being assigned a probability that is equal to the sum of theprobabilities of the two merged patterns. Said merging process may berepeated until all the N−Np patterns are merged.

Thereafter, the selected Np patterns may be converted to a reducednumber of patterns (e.g., Y patterns to be used in the repetitivecycle). This conversion may be achieved by finding integer numbersproportional to the probability of the pattern (or closer) where sum ofthe integer numbers is equal to Y and the smallest integer number is atleast one. If in the process, this condition cannot be met (i.e. if thesmallest integer number (rounded) is 0), the least probable pattern ismerged to the closest pattern of the remaining patterns. Thereafter, theprocess is repeated until the integer number corresponds to the lowestprobable pattern is at least one. After this process, each pattern isrepeated by its allocated integer number creating exactly Y number ofpatterns (there may be some duplicated patterns). In order to obtain thebest overall performance, it may be advantageous to spread out thoseduplicated patterns within the Y pattern.

The process for obtaining the common interference patterns may bemodified to account for temporal fading and other factors. Specifically,temporal fading may refer to a variation in signal attenuation withrespect to time, as may be attributable to the time-variant nature ofchannel characteristics (e.g., path loss floats due to multipathpropagation, shadowing, etc.). Notably, temporal fading may cause theindividual eNB-to-eNB interference components to fluctuate, which maycause the simulations used to obtain interference patterns to becomeunstable. To correct for this, a central controller may introduceup-fade margins (e.g., positive margins) and/or down-fade margins (e.g.,negative margins) prior to interference pattern optimization (e.g.,before narrowing the potential interference patterns into one or morecommon interference patterns). For instance, a set of X interferencepatterns (X is an integer) may be identified in accordance with longterm channel statistics. Thereafter, the central controller may apply anup-fade margin to the set of X interference patterns to obtain a set ofX up-fade adjusted interference patterns. Likewise, the centralcontroller may apply a down-fade margin to the set of X interferencepatterns to obtain a set of X down-fade adjusted interference patterns.The three sets of interference patterns may be aggregated to form thesuperset of 3X potential interference patterns, which may thereafter besubjected to statistical narrowing techniques to obtain one or morecommon interference patterns. In some embodiments, multiple up-fadeand/or down-fade margins may be used, to generate a larger superset ofinterference patterns. For instance, two up-fade margins (e.g., a largerone and a smaller one) and two down-fade margins (e.g., a larger one anda smaller one) may be applied to a set of X interference patterns togenerate a superset of 5X potential interference patterns.

FIG. 9 illustrates a block diagram of an embodiment PC controller 900.The PC controller 900 may include a backhaul interface 902, a controlinterface 903, a processor 904, and a memory 905, which may be arrangedas shown in FIG. 9. The backhaul interface 902 may be any component orcollection of components that allows the PC controller 900 to engage innetwork communications with another device, e.g., an eNB, another PCcontroller, etc. The control interface 903 may be any component orcollection of components that allows the PC controller 900 to engage innetwork communications with a network administrator. The processor 904may be any component capable of performing computations and/or otherprocessing related tasks, and the memory 905 may be any componentcapable of storing programming and/or instructions for the processor.

FIG. 10 illustrates a block diagram of an eNB 1000. The eNB 1000 mayinclude a backhaul interface 1002, a control interface 1003, a processor1004, a memory 1005, a transmitter 1006, a receiver 1008, a coupler1010, and an antenna 1012, which may be arranged as shown in FIG. 10.The backhaul interface 1002 may be any component or collection ofcomponents that allows the eNB 1000 to engage in network communicationswith another device, e.g., other eNBs, a PC controller, etc. The controlinterface 1003 may be any component or collection of components thatallows the eNB 1000 to engage in network communications with a networkadministrator. The processor 1004 may be any component capable ofperforming computations and/or other processing related tasks, and thememory 1005 may be any component capable of storing programming and/orinstructions for the processor. The transmitter 1006 may be anycomponent capable of transmitting a signal, while the receiver 1008 maybe any component capable of receiving a signal. The coupler 1010 may beany component capable of isolating a transmission signal from areception signal, such as a duplexer. The antenna 1012 may be anycomponent capable of emitting and/or receiving a wireless signal. In anembodiment, the eNB 1000 may be configured to operate in a long termevolution (LTE) network using an OFDMA downlink channel divided intomultiple subbands or subcarriers and using SC-FDMA in the downlink. Inalternative embodiments, other systems, network types and transmissionschemes can be used, for example, 1XEV-DO, IEEE 802.11, IEEE 802.15 andIEEE 802.16, etc.

Embodiments of this disclosure may be applicable to various coordinatedmultipoint (COMP) schemes and/or interference cancelation schemes, andbe modified to incorporate beamforming.

Although the present invention and its advantages have been described indetail, it should be understood that various changes, substitutions andalterations can be made herein without departing from the spirit andscope of the invention as defined by the appended claims. Moreover, thescope of the present application is not intended to be limited to theparticular embodiments of the process, machine, manufacture, compositionof matter, means, methods and steps described in the specification. Asone of ordinary skill in the art will readily appreciate from thedisclosure of the present invention, processes, machines, manufacture,compositions of matter, means, methods, or steps, presently existing orlater to be developed, that perform substantially the same function orachieve substantially the same result as the corresponding embodimentsdescribed herein may be utilized according to the present invention.Accordingly, the appended claims are intended to include within theirscope such processes, machines, manufacture, compositions of matter,means, methods, or steps.

What is claimed is:
 1. A method for facilitating uplink power control ina wireless network, the method comprising: obtaining a plurality ofpotential interference patterns between a plurality of neighboringcells, wherein each of the plurality of potential interference patternsspecify a different set of inter-cell-interference (ICI) thresholds forconstraining scheduled transmissions in the plurality of neighboringcells; statistically narrowing the plurality of potential interferencepatterns into one or more common interference patterns; and sending theone or more common interference patterns to one or more user equipments(UEs) in the wireless network, thereby triggering the one or more UEs toperform uplink power control based on the one or more commoninterference patterns.
 2. The method of claim 1, wherein obtaining theplurality of potential interference patterns comprises: receiving, by acontroller, channel statistics corresponding to the plurality ofneighboring cells in the wireless network; and generating the pluralityof potential interference patterns in accordance with the channelstatistics.
 3. The method of claim 2, wherein generating the pluralityof potential interference patterns comprises: identifying a plurality ofpotential scheduling scenarios in accordance with the channelstatistics; simulating joint power control (JPC) and joint scheduling(JS) for each of the potential scheduling scenarios; and obtaining theplurality of potential interference patterns by estimating levels ofinterference that would result from the simulated JPC and JS.
 4. Themethod of claim 3, wherein obtaining the plurality of potentialinterference patterns by estimating levels of interference that wouldresult from the simulated JPC and JS comprises: generating a first setof interference patterns according to the estimated levels ofinterference that would result from the simulated JPC and JS; generatinga second set of interference patterns by adjusting the estimated levelsof interference by fading margins; and identifying the plurality ofpotential interference patterns as including both the first set ofinterference patterns and the second set of interference patterns. 5.The method of claim 1, wherein each of the one or more commoninterference patterns specifies a plurality of ICI thresholds.
 6. Themethod of claim 5, wherein the plurality of ICI thresholds include aplurality of total interference thresholds, wherein each of theplurality of total interference thresholds specifies a maximum amount ofinterference to be produced in a corresponding one of the plurality ofneighboring cells as a result of uplink transmissions in each of theother neighboring cells.
 7. The method of claim 1, wherein statisticallynarrowing the plurality of potential of interference patterns comprises:merging correlated ones of the plurality of interference patterns withone another to generate a non-homogenous set of interference patterns.8. An apparatus for facilitating uplink power control in a wirelessnetwork, the apparatus comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions to: obtain aplurality of potential interference patterns between a plurality ofneighboring cells, wherein each of the plurality of potentialinterference patterns specify a different set of inter-cell-interference(ICI) thresholds for constraining scheduled transmissions in theplurality of neighboring cells; statistically narrow the plurality ofpotential interference patterns into one or more common interferencepatterns; and send the one or more common interference patterns to oneor more user equipments (UEs) in the wireless network, therebytriggering the one or more UEs to perform uplink power control based onthe one or more common interference patterns.
 9. A method for uplinkpower control, the method comprising: receiving, by a user equipment(UE), a common interference pattern from a central controller, thecommon interference pattern specifying interference thresholds formultiple neighboring base stations of a serving base station; receiving,by the UE, fade margins corresponding to the multiple neighboring basestations; and performing, by the UE, uplink power control for an uplinktransmission from the UE to the serving base station based on the commoninterference pattern and the fade margins.
 10. The method of claim 9,wherein the common interference pattern specifies an interferencethreshold for each of the multiple neighboring base stations.
 11. Themethod of claim 10, wherein performing uplink power control for theuplink transmission based on the common interference pattern comprises:selecting a transmission level for the uplink transmission that producesinterference levels at the neighboring base stations that are less thanthe respective interference threshold for that neighboring base station.12. The method of claim 9, wherein performing uplink power control basedon the common interference pattern and the fade margins comprisesapplying the fade margins to the common interference pattern to obtain amodified interference pattern, and using the modified interferencepattern to select a power level of the uplink transmission.
 13. Themethod of claim 9, further comprising receiving an indication ofresources that have been scheduled to carry the uplink transmission. 14.The method of claim 9, further comprising receiving an indication thatthe serving base station has been scheduled to receive the uplinktransmission.
 15. The method of claim 9, wherein the common interferencepattern is received from a central controller.
 16. A user equipment (UE)comprising: a processor; and a non-transitory computer readable storagemedium storing programming for execution by the processor, theprogramming including instructions to: receive a common interferencepattern from a central controller, the common interference patternspecifying interference thresholds for multiple neighboring basestations of a serving base station; receive fade margins correspondingto the multiple neighboring base stations; and perform uplink powercontrol for an uplink transmission from the UE to the serving basestation based on the common interference pattern and the fade margins.17. A method for facilitating uplink power control in a wirelessnetwork, the method comprising: obtaining a plurality of potentialinterference patterns between a plurality of neighboring cells, whereineach of the plurality of potential interference patterns specify adifferent set of inter-cell-interference (ICI) thresholds forconstraining scheduled transmissions in the plurality of neighboringcells; statistically narrowing the plurality of potential interferencepatterns into one or more common interference patterns; and sending theone or more common interference patterns to one or more user equipments(UEs) in the wireless network, thereby triggering the one or more UEs torequest uplink resource allocations based on the common interferencepatterns.
 18. The method of claim 17, wherein obtaining the plurality ofpotential interference patterns comprises: receiving, by a controller,channel statistics corresponding to the plurality of neighboring cellsin the wireless network; and generating the plurality of potentialinterference patterns in accordance with the channel statistics.
 19. Themethod of claim 18, wherein generating the plurality of potentialinterference patterns comprises: identifying a plurality of potentialscheduling scenarios in accordance with the channel statistics;simulating joint power control (JPC) and joint scheduling (JS) for eachof the potential scheduling scenarios; and obtaining the plurality ofpotential interference patterns by estimating levels of interferencethat would result from the simulated JPC and JS.
 20. The method of claim19, wherein obtaining the plurality of potential interference patternsby estimating levels of interference that would result from thesimulated JPC and JS comprises: generating a first set of interferencepatterns according to the estimated levels of interference that wouldresult from the simulated JPC and JS; generating a second set ofinterference patterns by adjusting the estimated levels of interferenceby fading margins; and identifying the plurality of potentialinterference patterns as including both the first set of interferencepatterns and the second set of interference patterns.
 21. The method ofclaim 20, wherein the fading margins are interference channel dependentand are determined in accordance with fading statistics provided by aplurality of base stations in the wireless network.
 22. The method ofclaim 17, wherein each of the one or more common interference patternsspecifies a plurality of ICI thresholds.
 23. The method of claim 22,wherein the plurality of ICI thresholds include a plurality of totalinterference thresholds, wherein each of the plurality of totalinterference thresholds specifies a maximum amount of interference to beproduced in a corresponding one of the plurality of neighboring cells asa result of uplink transmissions in each of the other neighboring cells.24. An apparatus for facilitating uplink scheduling in a wirelessnetwork, the apparatus comprising: a processor; and a non-transitorycomputer readable storage medium storing programming for execution bythe processor, the programming including instructions to: obtain aplurality of potential interference patterns between a plurality ofneighboring cells, wherein each of the plurality of potentialinterference patterns specify a different set of inter-cell-interference(ICI) thresholds for constraining scheduled transmissions in theplurality of neighboring cells; statistically narrow the plurality ofpotential interference patterns into one or more common interferencepatterns; and send the one or more common interference patterns to oneor more user equipments (UEs) in the wireless network, therebytriggering the one or more UEs to request uplink resource allocationsbased on the common interference patterns.
 25. A method for uplink powercontrol, the method comprising: receiving, by a user equipment (UE), acommon interference pattern, the common interference pattern specifyinginterference thresholds for multiple neighboring base stations of aserving base station; and selecting, by the UE, uplink resources tocarry an uplink transmission from the UE to the serving base stationbased on the common interference pattern; and sending a resource requestto the serving base station to request that the selected uplinkresources be scheduled to the UE.
 26. The method of claim 25, whereinthe common interference pattern specifies an interference threshold foreach of the multiple neighboring base stations.
 27. A user equipment(UE) comprising: a processor; and a non-transitory computer readablestorage medium storing programming for execution by the processor, theprogramming including instructions to: receive a common interferencepattern, the common interference pattern specifying interferencethresholds for multiple neighboring base stations of a serving basestation; and select uplink resources to carry an uplink transmissionfrom the UE to the serving base station based on the common interferencepattern; and send a resource request to the serving base station torequest that the selected uplink resources be scheduled to the UE.